Police in Seattle shot and killed a 30-year-old woman, who family members said was pregnant, on Sunday after she called 911 about a possible burglary — and now an investigation is underway into the officers' use of force.

The woman, who was identified in the Seattle Times by family members as Charleena Lyles, had a knife and interacted with two officers before she was shot, according to the Seattle Police Department.

Family members said Lyles had experienced mental health problems in the last year and that she was several months pregnant, which BuzzFeed News couldn't immediately confirm. Family members also said they believe race was a factor in the incident — Lyles was black, and the two police officers who shot her were white.

In a video posted by the Seattle Times, a woman who identified herself as Lyles' sister can be seen screaming into the camera distraught, telling the reporters that deadly force was not needed in the situation.

"She's this fucking tall," Monika Williams said, placing her hand below her head. "There's no reason for her to be shot, in front of her babies!" Williams said, adding later that the officers could have tased Lyles instead.

Seattle police confirmed that two boys and one girl, aged 11, 4, and 1, were in the apartment at the time of the shooting, and have since been given over to family members.

Audio taken from the officer's dashcam was released by police on Monday morning. The department, in a statement, said it believes "transparency throughout the investigation of deadly force incidents is essential to maintaining public trust."

In the audio, officers can be heard talking about responding to the burglary call in tandem because of "hazard information" regarding Lyles in the system, Det. Mark Jamieson said.

"While property crimes reports typically require only one officer to be dispatched, two officers were dispatched to this particular call for service because of a recent officer safety caution associated with the caller," a Seattle police statement said as to why the extra officer was warranted.

In the choppy audio, the unidentified officers discussed previous visits to Lyles' residence, before greeting her and asking to come into the apartment.

Lyles and the officers can be heard talking about the alleged burglary.

"This bag that I had open with my clothes and..." Lyles can be heard saying, before the audio becomes silent and, at times, indiscernible.

Suddenly, one of the officers can be heard saying: "Step back, step back!" The crying of a baby or child can be heard.

A woman's voice, presumably that of Lyles, can be heard saying: "You ready? Motherfucker."

"We need help," and "Get back! Get back!" the officers can be heard saying, before the loud sounds of multiple gunshots occur, and the audio abruptly stops.

Seattle's Mayor Ed Murray said the incident was a "tragedy for all involved and will be fully investigated."

Around 50 people reportedly held a vigil on Sunday evening outside the apartment complex where Lyles was shot, with photographs of Lyles, flowers and candles.

The shooting is being reviewed by the Seattle Police Department's Force Investigation Team, and its Office of Professional Accountability.

Talal Ansari is a reporter for BuzzFeed News and is based in New York. His secure PGP fingerprint is 4FEE 894C 8088 7E08 E170 A515 2801 7CC6 95D3 11C2